The First Minister was speaking at the annual dinner of the DUP’s Blossomhill Branch in Co Tyrone.

He said: “Even though they only have one minister in the Executive and 14 MLAs, the SDLP’s capacity to unnerve Sinn Fein is quite considerable. Too often Alex Attwood’s position one day is Sinn Fein’s the next. Or worse still, a fear of what the SDLP will say or do can often paralyse their ability to take decisions,” he argued.

Mr Attwood is seen as a key policy maker for the SDLP.

The DUP leader advised Sinn Fein that allowing “smaller parties to set the agenda, or to dictate your position, is the road to ruin”, adding “time and time again the SDLP takes a stance that Sinn Fein lacks the courage to oppose”.

He gave the recent welfare reform debate, when Sinn Fein unsuccessfully moved a motion to delay the introduction of changes put forward at Westminster which will reduce benefit payments, as an example.

“The truth is that they wanted the Bill to go through but they didn’t want to be seen voting for it.

“Lest there be any doubt about this it was exposed when the SDLP challenged Sinn Fein to sign a petition of concern which would have actually stopped the Bill. All of this makes one wonder what Sinn Fein was playing at by voting against it at its Second Stage when they clearly wanted the Bill to pass,” Mr Robinson said.

He went on to accuse Sinn Fein of “chicanery”. but was equally scathing about the SDLP.

The DUP leader said he believed that “an SDLP in terminal decline is not good news for unionists. It will simply mean that Sinn Fein will take a larger share of the nationalist vote”.

He advised SDLP leader Dr Alasdair McDonnell that his party “appears to be drifting to the left of politics” which he said was “fatally flawed” policy.

Sinn Fein South Belfast MLA Alex Maskey said: “Peter Robinson’s leadership credentials both within unionism and as a senior figure in government have been called into serious question in recent times, most particularly with respect to the Orange parades, unionist celebrations of the Covenant anniversary and the DUP attitude to the Tory Welfare cuts agenda.